This invention relates to earth drilling machines of the type having a mast, a drive, assembly movable along the mast, a boom mounted adjacent the mast to move between a lower boom position and an upper boom position, a plurality of boom clamps mounted to the boom to grip a length of down hole tubular, a tubular storage device at a lower level, and a lifter configured to move a length of down hole tubular between a lower lifter position aligned with the tubular storage device and an upper lifter position aligned with the lower boom position. In particular, this invention relates to an automatic sequencing system for such an earth drilling machine that automatically coordinates movements of the boom and the lifter.
As used herein the term "down hole tubular" is intended broadly to cover the full range of tubulars used in earth drilling and production operations, including drill pipes, casings, and production tubulars.
In the past, earth drilling machines of the type described above have been manually controlled to raise a tubular from the storage device via the lifter and the boom to the center line of the bore hole drilled by the drilling machine. Similarly, simple manual control has been used when lowering a tubular off of the bore hole axis and down to the storage device with the boom and the lifter.
Manual control of this type can be taxing on the operator, and operator mistakes can result in damage to the drilling equipment. Furthermore, it is difficult or even impossible for an operator to coordinate movement of the boom and the lifting device in a consistent manner so as to minimize the time required to transfer a tubular between the storage device and the center line of the bore hole.
An earth drilling machine of the type described above may in certain cases not be provided with an explosion proof electrical system in the vicinity of the bore hole. In such cases, the use of electrically powered sensors or actuators can result in explosion proof electric system can be avoided to the a considerable expense. The expense of such an extent that mechanically operated valves and sensors can be substituted for electrically operated valves and sensors. As used herein, the term "mechanically operated" is intended broadly to encompass lever actuation, cam actuation and hydraulic pilot pressure actuation.